This disclosure relates to turbomachinery, and more particularly, the disclosure relates to an active clearance control system for a gas turbine engine.
Gas turbine engines include a compressor that compresses air, a combustor that ignites the compressed air and a turbine across which the compressed air is expanded. The expansion of the combustion products drives the turbine to rotate, which in turn drives rotation of the compressor.
In order to increase efficiency, a clearance between the tips of the blades in the compressor, turbine and power turbine across the outer diameter of the flowpath is kept sufficiently small. This ensures that a minimum amount of air passes between the tips and the outer diameter. Some engines include a blade outer air seal (BOAS) supported by case structure to further reduce tip clearance.
The clearance between the BOAS and the blade tips is sensitive to the temperature of the gas path at different engine conditions. If the BOAS support structure heats up at a faster rate than the rotating blades, the tip clearance could increase and cause a drop in efficiency. Conversely, if the blades heat up at a faster rate than the BOAS support structure, the blades can undesirably rub against the BOAS. As a result, it is difficult to accommodate a consistent tip clearance during different power settings in the engine.
Active clearance control (ACC) systems have been developed to selectively direct cooling fluid at the case structure to more closely control the clearance between the BOAS and blade tips. A simpler, more effective ACC system is needed.
Inlet particle separators are used at an inlet of some gas turbine engines that are exposed to a large amount of dust and debris. The inlet particle separator is used to separate out the debris from the core flowpath. Separated debris-laden air is expelled directly out through exhaust.